Laminated glass has a variety of uses, such as in front, side and rear windshields of vehicles (e.g. automobiles) and windowpanes of aircraft, buildings, and the like, because it is a form of safety glass that is less likely to scatter even when shattered by external impact. A known example of laminated glass is a laminated glass including at least a pair of glass plates integrated through, for example, an interlayer film for laminated glass which contains a liquid plasticizer and a polyvinyl acetal resin.
A recent growing need is the development of a head-up display (HUD) that presents meters showing vehicle driving data (e.g. driving speed information) within a usual range of vision in the front windshield of a vehicle.
There have been known various types of HUDs. The most typical one is a HUD that is designed such that a display unit of an instrumental panel projects information (e.g. driving speed information) sent from a control unit onto a front windshield to enable a driver to view the information at a usual viewpoint, that is, within a usual range of vision in the front windshield.
An example of laminated glass interlayer films for a HUD is a wedge-shaped laminated glass interlayer film with a predetermined wedge shape proposed in Patent Literature 1. This interlayer film can solve a HUDs' problem that a meter image displayed on a laminated glass appears double.
Patent Literature 1 also discloses a laminated glass that is partially free from the HUDs' problem that a meter image appears double. Yet, not the entire surface of the laminated glass is free from the double meter image problem.
Patent Literature 2 discloses a laminated glass including a laminate of an interlayer containing hydroxy terephthalate between two transparent plates. Patent Literature 2 also discloses a laminated glass that produces a high contrast image under light radiation. Unfortunately, in the case of such a laminated glass including an interlayer containing hydroxy terephthalate, the interlayer is susceptible to color changes.